Well bore data transmission apparatus with debris clearing apparatus

ABSTRACT

In the representative embodiment of the apparatus of the present invention disclosed herein, a first ported or grooved cylindrical member is mounted within a drill string for directing drilling fluids flowing through the apparatus along one or more selected flow paths toward a second ported or grooved cylindrical member which is coaxially arranged in the drill string adjacent to the first member for rotation in a transverse plane cutting the flow paths to cyclically obstruct these flow paths. An electric motor is cooperatively coupled by a shaft to the rotatable member for driving the member at a selected speed to develop an acoustic signal of a desired frequency as the flow paths are momentarily obstructed at periodic intervals. To prevent jamming of the rotating member should debris carried in the circulating drilling fluid become lodged between the two signal-producing members, the rotating member is slidably mounted on the shaft to move away from the fixed member in response to a significant increase of the pressure differential across the two members as might occur by an accumulation of debris or the like therebetween tending to at least slow the rotating member. Biasing means maintain the rotating member in its normal position as well as restore the rotating member to its normal operating position adjacent to the fixed member once the debris has been cleared from between the signal-producing members by the continued flow of the drilling fluid. Control means are also provided for alternately reversing the motor whenever the rotational speed of the motor significantly decreases.

trite Sttes tet [191 Anderson Oct. 9, 1973 WELL BORE DATA TRANSMISSIONAPPARATUS WlTH DEBRIS CLEARING APPARATUS [75] Inventor: Ronald A.Anderson, Seabrook,

Tex.

[73] Assignee: Schlumberger Technology Corporation, New York, NY.

Filed: June 15, 1972 Appl. No.: 263,022

Primary ExaminerBenjamin A. Borchelt Assistant Examinerl-l. A. BirmielAttorney-Ernest R. Archambeau, Jr. et al.

[5 7] ABSTRACT In the representative embodiment of the apparatus of thepresent invention disclosed herein, a first ported or groovedcylindrical member is mounted within a drill string for directingdrilling fluids flowing through the apparatus along one or more selectedflow paths toward a second ported or grooved cylindrical member which iscoaxially arranged in the drill string adjacent to the first member forrotation in a transverse plane cutting the flow paths to cyclicallyobstruct these flow paths. An electric motor is cooperatively coupled bya shaft to the rotatable member for driving the member at a selectedspeed to develop an acoustic signal of a desired frequency as the flowpaths are momentarily obstructed at periodic intervals. To preventjamming of the rotating member should debris carried in the circulatingdrilling fluid become lodged between the two signal-producing members,the rotating member is slidably mounted on the shaft to move away fromthe fixed member in response to a significant increase of the pressuredifferential across the two members as might occur by an accumulation ofdebris or the like therebetween tending to at least slow the rotatingmember. Biasing means maintain the rotating member in its normalposition as well as restore the rotating member to its normal operatingposition adjacent to the fixed member once the debris has been clearedfrom between the signal-producing members by the continued flow of thedrilling fluid. Control means are also provided for alternatelyreversing the motor whenever the rotational speed of the motorsignificantly decreases.

29 Claims, 5 Drawing Figures SIGNAL DETECTOR PAIENIEU BET 9 I973PATENTED 9 I973 SHEET 2 BF 2 FIG.4

2Q SQUARE WAVE SUPPLY COMPARATOR REFE'RENCE RECT.

TACH.

FIGS

WELL BORE DATA TRANSMISSION APPARATUS WITH DEBRIS CLEARING APPARATUSVarious downhole signaling devices have been proposed heretofore fortransmitting data representative of one or more downhole conditions tothe surface during the drilling of a borehole. One of the morepromisingdevices of this nature is a fluid-dynamic transducer or a so-calledsiren (such as shown generally at 62 in U.S. Pat. No. 3,309,656) that isselectively arranged for developing acoustic signals which aretransmitted to the surface through the circulating mud stream in thedrill string. A typical one of these sirens includes a grooved or portedrotor which is rotatively driven at one or more selected speeds acrossone orm'ore jets of drillingmud issuing from a fixed groove or portedstator for producing acoustic signals at fre quencies related to thedesign of the siren members, the properties of the drilling mud, and therotational speed of the rotor. Thus, by selectively controlling therotational speed of the rotor in accordance with variations in ameasured downhole condition, the siren can be selectively operated asrequired for transmitting coded acoustic signals to the surface whichare representative of the measurements of the downhole condition.

Although sirens such as these have other advantages, one of theparamount advantages in using these signaling devices is that acousticsignals can be efficiently produced thereby within a frequency span ofabout to BOO-cycles/second. As noted in the aforementioned patent,frequencies above this range are subject to significant attenuation; andit is, therefore, preferred to operate these sirens to produce signalsat frequencies between about 10 to 60-cycles/second. Although signalingdevices such as these have shown significant promise for commercialapplications, the narrow spacing between the two siren members requiredto produce satisfactory acoustic signals makes these sirens particularlysusceptible to being jammed or easily obstructed either by drilling mudsolids or by well debris and the like which is prevalent in thecirculating mud stream in a typical borehole.

Accordingly, it is an object of the present invention to provide a newand improved well bore datatransmission system for producing selectivelycoded acoustic signals in a selected frequency range in debrisbearingwell bore fluids such as a circulating stream of drilling mud.

This and other objects of the present invention are attained byproviding a well tool adapted to be connected in a pipe string such as adrill string having a drill bit dependently coupled thereto and arrangedfor excavating a borehole as a drilling fluid is circulated through afluid passage in the tool and the drill string. To generate distinctiveacoustic signals in the circulating fluid representative of one or moredownhole measurements, acoustic signaling means on the tool include aselectively controlled electric motor rotatively driving aflow-controlling member arranged to be positioned immediately adjacentto another flowcontrolling member within the fluid passage so as tocyclically vary the degree of flow obstruction presented by the twoflow-controlling members in cooperation with one another for producingan acoustic signal. The acoustic signaling means further include controlmeans responsive to an operating condition, such as an increasedpressure drop across the two members, which is indicative of slowing ofthe motor for temporarily separating the flow-controlling members so asto allow debris and the like to be carried free of the two members bythe flowing mud stream. The control means are further responsive to thecessation of the operating condition causing slowing of the motor, suchas a decrease in the pressure differential to its usual operating range,for restoring the flow-controlling members to their signal-producingpositions once debris has been freed from between the two members. Meansare further provided for selectively reversing the rotational directionof the rotating member as a further aid in clearing debris and othersolid materials from the acoustic signaling means.

The novel features of the present invention are set forth withparticularity'in the appended claims. The invention, together withfurther objects and advantages thereof, may be best understood by way ofthe following description of exemplary apparatus employing theprinciples of the invention as illustrated in the accompanying drawings,in which:

FIG. 1 shows a new and improved well tool arranged in accordance withthe present invention as it will appear while coupled in a drill stringduring the course of a typical drilling operation;

FIG. 2 depicts a preferred embodiment of the acoustic signaler employedwith the well tool shown in FIG.

FIGS. 3 and 4 are cross-sectional views respectively taken along thelines 3-3 and 4-4 in FIG. 2; and

FIG. 5 schematically illustrates a representative control circuit whichmay be employed in the present invention.

Turning now to FIG. 1, a new and improved well tool 10 arranged inaccordance with the present invention is depicted coupled in a typicaldrill string 11 having a rotary drill bit 12 dependently coupled theretoand adapted for excavating a borehole 13 through various earthformations as at 14. As the drill string 11 is rotated by a typicaldrilling rig (not shown) as the surface, substantial volumes of thedrilling fluid or socalled mud are continuously pumped downwardlythrough the tubular .drill string and discharged from the drill bit 12to cool the bit as well as to carry earth borings removed by the bit tothe surface as the mud is returned upwardly along the borehole l3exterior of the drill string. As is typical, the mud stream iscirculated by employing one or more high-pressure mud pumps (not shown)which continuously draw the fluid from a storage pit or surface vessel(not shown) for subsequent recirculation by the mud pumps. It will beappreciated, therefore, that the circulating mud stream flowing throughthe drill string 11 serves as a transmission medium that is well suitedfor transmitting acoustic signals to the surface at the speed of soundin the particular drilling fluid.

In accordance with the principles of the present invention,data-transmitting means 15 are arranged on the well tool 10 and includeone or more conditionresponsive devices, as at 16 and 17, respectivelycou pled to an appropriate measurement encoder l8 operatively arrangedto produce a series of electrical coded data signals that arerepresentative of the measurements being obtained by thecondition-responsive devices. Although a self-contained battery powersupply could be employed, as shown at 19 it is preferred to employ areaction-type turbine driving a generator for utilizing the circulatingmud stream as a motivating source to generate electric power foroperation of the new and improved data-transmitting means 15. As willsubsequently be explained in greater detail, the datatransmitting meansfurther include acousticsignaling means including an electric motor 21coupled to the encoder l8 and operatively arranged to respond to itscoded output signals for rotatively driving an acoustic signaler 22 byway of a typical gear train 23 to successively interrupt or obstruct theflow of the drilling fluid through the drill string 11. The resultingacoustic signals produced by the acoustic signaler 22 will betransmitted to the surface through the mud stream flowing within thedrill string 11 as encoded representations or data signals indicative ofthe one or more downhole conditions respectively sensed by thecondition-measuring devices 16 and 17. As these data signals aresuccessively transmitted to the surface, they are detected and convertedinto meaningful indications or records by suitable acoustic signaldetecting-andrecording apparatus 24 such as that disclosed in eitherU.S. Pat. No. 3,309,656, U.S. Pat. No. 3,488,629, or U.S. Pat. No.3,555,504.

Turning now to FIG. 2, a cross-sectioned elevational view is shown of apreferred embodiment of the new and improved acoustic signaler 22. Asseen there, the tool 10 includes a tubular body 25 which iscooperatively arranged in a typical manner with appropriate endconnections (not shown) to allow the body to be tandemly coupled in thedrill string 11. The tubular body 25 includes an axial fluid passage 26for conducting the drilling fluid flowing through the drill string 11 tothe drill bit 12 therebelow. As illustrated in FIGS. 2 and 3, the newand improved acoustic signaler 22 includes an annular ported orinternally grooved flowdirecting member 27 which is coaxially arrangedwithin the flow passage 26 and secured to the body 25 as by a set ofcomplementary threads 28. As will subsequently be explained in greaterdetail, in the preferred embodiment of the acoustic-signaling means 20the flow-directing member 27 is provided with a plurality of flowpassages defined by inwardly opening longitudinal grooves, as at 29,having a substantially rectangular or square cross-sectionalconfiguration which are respectively cut at equal circumferentiallyspaced intervals around the interior wall of the flow-directing memberparallel to and at a uniform radius from the longitudinal or centralaxis 30 of the tool body 25. To minimize turbulence and otherdisturbances to the flow of the downwardly flowing drilling fluidthrough the tool 10, the upper face of the flow-directing member 27 isconcavely shaped as at 31.

As best seen in FIGS. 2 and 4, in its preferred embodiment the acousticsignaler 22 further includes a rotatable ported or externally groovedflow-obstructing member 32 which is cooperatively arranged on the upperend of the output shaft 33 of the gear train 23 and coaxially disposedwithin the central fluid passage 26 for rotation in a transverse planeof rotation normally lying immediately below the flow-directing member27. As illustrated in FIG. 2, the opposed lower and upper faces 34 and35 of the flow-directing member 27 and the rotating flow-obstructingmember 32, respectively, are preferably made flat so as to respectivelylie in parallel transverse planes which are perpendicular to thelongitudinal axis 30 of the tool body 25 and are normally spaced a veryclose distance apart which, in the preferred embodiment of the presentinvention, is in the order of 0.020 to 0.030-inches.

As best seen in FIGS. 3 and 4, in the preferred embodiment of theacoustic signaler 22, the exterior of the rotating flow-obstructingmember 32 is provided with a number of longitudinal grooves 36 which arecooperatively shaped to define a plurality of equally spaced, outwardlydirected radial projections, as at 37, respectively having asubstantially rectangular or square configuration. Although differentdimensions and shapes, relative numbers, and relative proportions may beused for the grooves 29 and the projections 37 of the flowcontrollingmembers, it is preferable that the rotating member 32 be substantiallycomplementally shaped with respect to the interior opening of theflowdirecting member 27. In this manner, when the. flow obstructingmember 32 is angularly oriented with respect to the flow-directingmember 27 so as to align the projections 37 with the grooves 29, therewill be a substantial momentary obstruction to the flow of thecirculating mud stream through the tool 10. As pointed out in theaforementioned U.S. Pat. No. 3,309,656, by making the several grooves 29and the projections 37 substantially square or rectangular, rotation ofthe flow-obstructing rotor 32 in relation to the flowdirecting stator 27will repetitively obstruct the fluid passage 26 to a substantial degreeand then re-open the passage as the radial projections are progressivelymoved into registration and then out of alignment with the grooves forproducing cyclically varying sinusoidal pressure signals in the flowingdrilling mud of significant amplitude at the design fundamentalfrequency. In other words, by virtue of the rectangular or squareconfigurations of the grooves 29 and the radial projections 37, theeffective flow area for the drilling mud passing through the tool 10will vary continuously in a linear fashion so as to minimize theunwanted generation of acoustic signals of significant amplitudes athigh-order harmonic frequencies.

Of particular significance to the present invention, it will beappreciated that instead of being fixed to its driving shaft as is thecase for the siren disclosed in the aforementioned U.S. Pat. No.3,309,656, the flowobstructing member 32 is slidably mounted on theshaft 33 and co-rotatively coupled thereto as by one or morecomplementary longitudinal splines and grooves, as at 38, which arecooperatively arranged to permit the rotor to also slide longitudinallyalong the shaft between its normal elevated position as depicted in FIG.2 and at least one other relatively lower position where the rotor ismore distant from the flow-directing member 27. To define the uppermostposition of the rotor 32 in relation to the stator 27, the upper face 35of the rotor is counterbored, as at 39, for complementally receiving anenlarged shoulder 40 on the uppermost end of the shaft 33. Biasingmeans, such as a compression spring 41 having a predetermined springforce mounted around the shaft 33 between the gear-reduction unit 23 andthe lower face of the flow-obstructing member 32, are cooperativelyarranged for normally urging the rotating member upwardly toward theflow-directing member 27 so as to normally maintain the opposed faces 34and 35 of the two members closely spaced under usual flow conditions. Asdepicted, it is preferred that the lower end of the spring 4E besupported by a fixed shoulder 42 on the shaft 33 and having its lowerface slidably engaged with the upper end of the gearreduction unit 23.

Accordingly, it will be appreciated that the biasing force provided bythe spring 41 will be selected to maintain the flow-controlling members27 and 32 at their desired longitudinal spacing in relation to oneanother for producing acoustic signals of a desired characteristicduring the normal operation of the acoustic signaler 22. However, shouldthere be a downwardly acting force on the rotating member sufficient toovercome the upwardly-directed biasing action of the spring 41, theflow-obstructing member 32 will be moved downwardly along the shaft 33until such time that the downwardly acting forces on the rotating memberare countered by the upwardly acting force imposed by the furthercompression of the spring.

in the normal course of operation of the acousticsignaling means of thepresent invention, the flow obstructing member 32 will be rotated at aselected constant speed for producing alternating acoustic signalshaving a waveform dictated by the shapes of the openings 29 and theprojections 37 and at a frequency which is determined by the rotationalspeed of the rotating member as well as the number of the openings andprojections. As various borehole conditions being measured by themeasuring devices 16 and 17 change during the course of the drillingoperation, the data encoder 18 will be effective for controlling themotor 21 so as to produce, for example, signals of different frequenciessuch as described in detail in the aforementioned U.S. Pat. No.3,309,656. lt will, of course, be appreciated that othersignal-transmission modes may also be employed with thedata-transmitting means 15. For example, by momentarily operating themotor 21 so as to either retard or advance the rotation of theflow-obstructing member 32, the phase relationship of the resultingoutput acoustic signal may be selectively varied sufficiently either inrelation to previous output signals or in relation to a constantreference signal for producing other forms of distinctive acousticsignals which are also representative of the borehole conditions beingmonitored by the measuring devices 16 and 17. It will, of course beappreciated that the details of such selective regulation of the motor21 for driving the flow-obstructing member 32 to provide a giventransmission mode are not necessary for an understanding of theprinciples of the present invention.

Accordingly, in the usual situation, the flowobstructing member 32 issteadily rotated at a speed governed by the operation of the drivingmotor 21. So long as the flow-obstructing member 32 is free to rotatewith relation to the flow-directing member 27, the acoustic signalsproduced by the acoustic signaler 22 will be transmitted to the surfaceby way of the drilling fluid within the drill string 11 for detectionand recording by the surface apparatus 24. However, as it is not at alluncommon, debris and the like which is commonly found in a borehole,such as at 13, during a typical drilling operation will be swept to thesurface along with the returning drilling mud where significant portionsof such debris will be picked up by the mud pumps and discharged intothe drill string 11. As a result, those skilled in the art willappreciate that it is quite likely that pieces of wire, sticks, andother solid foreign materials will, from time to time, enter one or moreof the grooves 29 in the flow-directing member 27 and must be carriedpast the rotating member 32 if rotation of the rotor is to continueHowever, all too frequently, it has been found that the torque appliedto the flow-obstructing member is insufficient to cut or break debriswhich is spanning the flow-controlling members 27 and 32 at any givenmoment. Thus, when this situation arises with a signaling device such asthat shown in the aforementioned U.S. Pat. No. 3,309,656, the rotordescribed there will be easily jammed to halt the further operation ofthat signaling device.

In keeping with the objects of the present invention, however, the newand improved acoustic signaler 22 is cooperatively arranged foroperation of a debris-laden drilling mud. Thus, with theacoustic-signaling means 20 of the present invention, should debris suchas a piece of wire or a stick become lodged in two openings, as at 29and 37, which are then aligned and thereby halt the flow-obstructingmember 32 in a slightly-advanced angular position where these twoopenings are then substantially out of registration, the resultingincreased pressure differential in the flowing stream of drilling fluidwill be effective for longitudinally shifting the rotating memberdownwardly along its cooperative spline and groove arrangement 38 on theshaft 33 to open an increased flow area for the passage of debris pastthe acoustic signaler 22. It will be recognized that as theflow-obstructing member 32 moves further away from the flow-directingmember 27, the motor 21 will correspondingly turn the rotating memberslightly as permitted by the length and rigidity of the piece of debristhat is then lodged in the acoustic signaler 22. In some instances,separation of the flow-controlling members 27 and 32 will be sufficientfor pulling the piece of jamming debris free of the flow-directingmember so that the continuing flow of the drilling mud will be effectivefor washing the debris out of the acoustic signaler 22 to restore therotational freedom of the rotating member. Thus, once a piece of debrishas been cleared from the acoustic signaler 22, the flow-obstructingmember 32 will be freed and the upwardly-directed biasing action of thespring 41 will be effective for returning the rotating member to itsnormal position immediately below the flow-directing member 27. Thus,the operation of acoustic-signaling means 20 will continue as beforeuntil the acoustic signaler 22 again becomes temporarily jammed byadditional debris.

It should be further noted at this point that there may well be debriswhich cannot be dislodged by simply shifting the flow-obstructing member32 downwardly in relation to the flow-directing member 27. Ordinarily,this would result in a permanent jamming of the acoustic signaler 22since the continued torque applied by the motor 21 on the piece ofdebris linking the flowcontrolling members 27 and 32 will simplymaintain the debris in a jamming position. However, by virtue of theability of the flow-controlling members 27 and 32 to separate, it willbe appreciated that by reversing the rotation of the motor 21, therespective openings, as at 29 and 37, into which the piece of debris hasbeen lodged can be returned into registration with one another formomentarily positioning a piece of jamming debris in a generallyparallel relation to the longitudinal axis 30 so as to hopefully permitthe correspondingly increased flow of drilling mud to dislodge thedebris. On the other hand, should this fail, reverse rotation of theflowobstructing member 32 will pull the debris in a different directionand hopefully dislodge the debris.

In any event, once the piece of jamming debris has been cleared from theacoustic signaler 22, the flowobstructing member 32 will be quicklyreturned by the spring 41 to its usual position immediately below theflow-directing member 27. Once this happens, the acoustic signal will ofcourse, be restored to continue the transmission of data or informationsignals to the surface. It should be noted that clearing of the debriswill also flush away any accumulation of drilling mud solids on thejammed flow-controlling members 27 and 32 which will occur when the twomembers are halted in a misaligned position.

It will, of course, be appreciated that various circuits can be providedto selectively reverse the driving motor 21 for attaining the objects ofthe present invention. However, in the preferred embodiment of thedatatransmitting means of the present invention, motor control circuitry43 such as depicted in FIG. 5 is cooperatively arranged for alternatelyreversing the rotation of the motor 21 back and forth so long as thespeed of the motor is below a desired operational level. As shown there,the motor 21 is a two-phase induction motor which is selectively drivenin either rotational direction by a conventional two-phase square-wavepower supply 44 coupled to typical driver circuits 45 connected to thetwo windings of the motor. To accomplish the alternate reversals of themotor 21, a typical reversing switch 46, such as a relay or suitablelogic gates, is arranged to selectively reverse the leads to one of themotor windings.

To control the reversing switch 46, a typical tachometer 47 is coupledto the shaft 48 of the motor 21 and cooperatively arranged for producingan output voltage which is proportional to the rotational speed of themotor. This output voltage is preferably rectified and filtered, as at49, and supplied to one input of a comparator 50 having a referencevoltage, as at 51, supplied to its other input. The output of thecomparator 50 is connected to one input of a gate, such as a NAND gate52, having its output connected to the input of a counter 53. The otherinput of the gate 52 is connected to one of the outputs of the powersupply 44 to provide a source of pulses. Any selected one of the outputsof the counter 53 is connected to the reversing switch 46.

Accordingly, in normal operation of the signaler 22, the speed of themotor 21 will be sufficient to maintain the output voltage of thetachometer 47 of such a magnitude that there will be no output signalfrom the comparator 50. This will correspondingly disable the gate 52 sothat there will be no output pulses supplied to the counter 53. Once,however, the motor 21 slows such as when the acoustic signaler 22 firstjams, the output voltage of the tachometer 47 will drop so as to producean output signal from the comparator 50 which, in turn, enables the gate52. Once the gate 52 is enabled, the pulses from the power supply 44will be supplied to the counter 53. Thus, each time the number of pulsessupplied to the counter 53 reach a number capable of producing an outputsignal at the connected output of the counter, the reversing switch 46will be energized or activated to reverse the rotation of the motor 21.The pulses will, of course, continue to be supplied to the counter 53 solong as the speed of the motor 21 is below its normal range. This will,therefore, accomplish a second reversal of the motor 21 once there is asubsequent output from the counter 53 which again energizes or activatesthe reversing switch 46. Thus, reversal of the motor 21 will be repeatedat frequent intervals such as every few seconds or so as long as thetachometer 47 indicates that the speed of the motor is below its normaloperating speed and accordingly maintains the gate 52 in an enabledstate.

Accordingly, it will be appreciated that the present invention hasprovided new and improved well bore apparatus for transmittinginformation or data signals representative of one or more downholeconditions to the surface during the course of a drilling operation. Byarranging the acoustic-signaling means of the present invention toinclude a rotating flow-obstructing member which is cyclically rotatedin the proximity of the flowdirecting member as the drilling fluid iscirculated past these members, an acoustic signal of a frequency relatedto the design of these members and the rotational speed of the rotatingmember is produced. To prevent debris and the like which is typicallycarried in a circulating stream of drilling mud from jamming thesignaling means, the rotating member is cooperatively arranged florsliding movement in relation to its supporting shaft to for theflow-controlling members to be separated thereby opening the normalclose spacing between the two members a sufficient amount to allow thedrilling fluid to wash the debris free of the acousticsignaling means.Biasing means are cooperatively arranged for restoring the rotatingmember to its normal position once the piece of jamming debris has beencleared from the acoustic-signaling means.

While only a particular embodiment of the present invention has beenshown and described, it is apparent that changes and modifications maybe made without departing from this invention in its broader aspects;and therefore, the aim in the appended claims is to cover all suchchanges and modifications as fall within the true spirit and scope ofthis invention.

What is claimed is:

1. Apparatus adapted for transmitting data signals from a well bore tothe surface and comprising:

a body adapted for connection in a pipe string and having a fluidpassage arranged to carry debrisbearing fluids between the surface andwell bore;

first means including a first signal-producing member cooperativelyarranged in said fluid passage for directing at least a portion of afluid flowing therethrough along at least one selected flow path;

second means including a second signal-producing member cooperativelyarranged in said fluid passage adjacent to said first member forrotation at a selected speed in a plane transverse to said flow path forrepetitively obstructing said flow path at periodic intervals tocyclically produce acoustic data signals in a fluid flowing through saidfluid passage; and

third means operable upon at least slowing of said second member belowsaid selected speed by fluidborne solids flowing through said fluidpassage for momentarily separating said signal-producing members toallow such solids to pass downstream ofsaid signal-producing members.

2. The apparatus of claim 1 wherein said second means include anelectric motor, and means cooperatively coupling said second member tosaid motor for rotation thereby as well as for movement between anoperating position adjacent to said first member and a solids-clearingposition more distant therefrom; and said third means include biasingmeans cooperatively arranged for yieldably urging said second membernormally toward one of its said positions.

3. The apparatus of claim 2 wherein said one position is said operatingposition of said second member.

4. The apparatus of claim 1 wherein said second means include anelectric motor, and means cooperatively coupling said second member forrotation thereby; and said third means include means cooperativelyarranging one of said members for longitudinal movement relative to theother of said members between an operating position adjacent to saidother member and a solids-clearing position more distant therefrom, andbiasing means cooperatively arranged for normally urging said one membertoward said other member and yieldable in response to slowing of saidsecond member below said selected speed by fluidborne solids forallowing said one member to move longitudinally away from said othermember.

5. The apparatus of claim 1 wherein said second means include anelectric motor, a rotatable shaft drivingly coupled to said motor, meanscooperatively cou pling said second member to said shaft for rotationthereby as well as for movement therealong between a signal-producingposition adjacent to said first member and a solids-clearing positionmore distant therefrom; and said third means include biasing meanscooperatively arranged between said shaft and said second member fornormally biasing said second member toward its said signal-producingposition and yieldable in response to at least one operating conditioncharacteristic of the rotational slowing of said second member forallowing said second member to move at least momentarily toward its saidsolids-clearing position.

6. The apparatus of claim 1 wherein said second means include aselectively reversible electrical motor, a rotatable shaft drivinglycoupled to said motor, and means cooperatively coupling said secondmember to said shaft for rotation thereby as well as for movementtherealong between a first position adjacent to said first member and atleast a second position more distant therefrom; and said third meansinclude biasing means cooperatively arranged between said shaft and saidsecond member normally biasing said second member toward its said firstposition and yieldable in response to slowing of said second member forallowing said second member to move at least momentarily toward its saidsecond position, and circuit means responsive to the slowing of saidsecond member for selectively re versing the rotational direction ofsaid motor.

7. The apparatus of claim 1 wherein said second means include aselectively reversible electrical motor, a rotatable shaft drivinglycoupled to said motor, means cooperatively coupling said second memberto said shaft for rotation thereby as well as for movement therealongbetween a first position adjacent to said first member and at least asecond position more distant therefrom; and said third means includebiasing means cooperatively arranged between said shaft and said secondmember normally biasing said second member toward its said firstposition and yieldable in response to slowing of the rotational speed ofsaid second member for allowing said second member to move at leastmomentarily toward its said second position, and circuit meansresponsive to the slowing of said second member and selectively operablefor alternately reversing the rotational direction of said motor backand forth so long as said second member is slowed below said selectedspeed.

8. Apparatus adapted for transmitting data to the sur face during thedrilling of a borehole and comprising:

a body adapted for connection in a tubular drill string and having afluid passage arranged to conduct drilling fluids to a borehole-drillingdevice depen dently coupled therebelow;

a flow-directing member cooperatively arranged in said fluid passage andincluding at least one opening for directing drilling fluids flowingthrough said fluid passage along a selected axis;

a flow-obstructing member cooperatively arranged in said fluid passagefor rotation in a plane transverse to said axis and including aplurality of alternately disposed openings and obstructions angularlyspaced from one another and respectively adapted to successively cutacross said axis upon rotation of said flow-obstructing member;

first means cooperatively coupled to said flowobstructing member forrotating said flowobstructing member at at least one selected rotationalspeed for cyclically producing acoustic data signals in drilling fluidsflowing through said fluid passage; and

second means operable in response to at least slowing of saidflow-obstructing member by lodging of fluid-borne debris between saidmembers for moving at least one of said members in relation to the otherof said members to allow such debris to be carried downstream of saidmembers by drilling fluids flowing through said fluid passage.

9. The apparatus of claim 8 wherein said one member is saidflow-obstructing member.

10. The apparatus of claim 9 wherein said first means include motormeans; and said second means include control means coupled to said motormeans and responsive to slowing of said flow-obstructing member belowsaid selected speed for rotatively moving said flow-obstructing memberback and forth in relation to said flow-directing member so long as saidflowobstructing member is slowed below said selected speed.

11. The apparatus of claim 9 wherein said first means include areversible electric motor; and said second means include circuit meansoperable upon slowing of said motor means for producing an electricalsignal, and control means responsive to said signal for repetitivelyreversing said motor.

12. The apparatus of claim 9 wherein said first means include a motor,and a rotatable shaft cooperatively coupled to said motor for rotationthereby; and said second means include means co-rotatively coupling saidflow-obstructing member to said shaft for rotation thereby as well asfor movement along said shaft between a first position adjacent to saidflow-directing member and a second more-distant position away from saidflow-directing member, and biasing means normally urging saidflow-obstructing member toward its said first position and yieldable inresponse to the occurrence of an operational condition indicative of thelodging of fluid-borne debris between said members for allowing saidflow-obstructing member to move at least momentarily toward its saidsecond position.

13. The apparatus of claim 12 wherein said operational condition is anincreased pressure differential llll across said members sufficient tomove said flowobstructing member toward its said second position.

14. The apparatus of claim 12 wherein said second means further includecontrol means coupled to said motor and responsive to slowing of saidflowobstructing member below said selected speed for rotatively movingsaid flow-obstructing member back and forth in relation to saidflow-directing member so long as said flow-obstructing member is slowedbelow said selected speed.

15. The apparatus of claim 9 wherein said first means include a motor,and a rotatable shaft cooperatively coupled to said motor for rotationthereby; and said second means include means co-rotatively coupling saidflow-obstructing member to said shaft for rotation thereby as well asfor longitudinal movement along said shaft between a first positionadjacent to said flowdirecting member and a second more-distant positionaway from said flow-directing member, and biasing means normally urgingsaid flow-obstructing member toward its said first position andyieldable in response to the occurrence of an operational conditionindicative of the lodging of fluid-borne debris between said members forallowing said flow-obstructing member to move at least momentarilytoward its said second position.

16. Apparatus adapted for measuring at least one downhole conditionwhile drilling a borehole and comprising:

a body tandemly coupled in a tubular drill string having aborehole-drilling device dependently coupled thereto and defining afluid passage for circulating drilling fluids between the surface andsaid borehole-drilling device;

data-signaling means on said body and adapted for producing electricalsignals representative of at least one downhole condition;

acoustic signaling means on said body and including an electric motorcoupled to said data-signaling means for selective rotation in responseto said electrical signals, a flow-directing member in said fluidpassage and having a plurality of angularly spaced openingscooperatively arranged for directing drilling fluids in selected fluidpaths along said fluid passage, and a rotatable signaling member in saidfluid passage and having a plurality of alternately distributedangularly-spaced openings and obstructions cooperatively arranged tosuccessively cross said fluid paths upon rotation of said signalingmember for producing cyclic acoustic signals representative of saidelectrical signals in drilling fluids flowing through said fluidpassage;

first means cooperatively coupling said signaling member to said motorfor rotation thereby at at least one selected rotational speed; and

second means operable upon slowing of said signaling member below saidselected rotational speed by lodging of fluid-borne materials betweensaid members for moving said signaling member in relation to saidflow-directing member to clear such fluidborne materials fromtherebetween.

17. The apparatus of claim 16 wherein said first means include arotatable shaft coupled to said motor; and

said second means include means co-rotatively coupling said signalingmember to said shaft, and control means coupled to said motor andresponsive to slowing of said signaling member below said selected speedfor alternately driving said motor back and forth in opposite rotativedirections so long as said signaling member is slowed below saidselected speed.

18. The apparatus of claim 16 wherein said signaling member isdownstream of said fluid-directing member.

19. The apparatus of claim H8 wherein said first means include arotatable shaft coupled to said motor;

and

said second means include means co-rotatively coupling said signalingmember to said shaft, and means operable upon increased pressuredifferentials across said members for shifting said signaling memberalong said shaft away from said flowdirecting member and operable uponthe subsequent decrease in such increased pressure differentials forshifting said signaling member along said shaft toward saidflow-directing member.

20. The apparatus of claim 19 wherein said second means further includemeans co-rotatively coupling said signaling member to said shaft, andcontrol means coupled to said motor and responsive to slowing of saidsignaling member below said selected speed for alternately driving'saidmotor back and forth in opposite rotative directions so long as saidsignaling member is slowed below said selected speed.

21. The apparatus of claim 16 wherein said flowdirecting member is fixedin relation to said body and is coaxially arranged in said fluidpassage.

22. The apparatus of claim 16 wherein said flow directing member isupstream of said signaling member.

23. The apparatus of claim 22 wherein said first means include arotatable shaft coupled to said motor; and said second means includemeans co-rotatively coupling said signaling member to said shaft forrotation thereby as well as for movement along said shaft between afirst position adjacent to said flow-directing member and a secondmore-distant position away from said flow-directing member, and biasingmeans normally urging said signaling member toward its said firstposition and yieldable in response to the occurrence of an operationalcondition indicative of the lodging of fluid-borne debris between saidmembers for allowing said signaling member to move at least momentarilytoward its said second position.

24. The apparatus of claim 23 wherein said operational condition is anincreased pressure differential across said members sufficient to movesaid signaling member toward its said second position.

25. The apparatus of claim 24 wherein said second means further includecontrol means coupled to said motor and responsive to slowing of saidsignaling member below said selected speed for alternately driving saidmotor back and forth in opposite rotative directions so long as saidsignaling member is slowed below said selected speed.

26. The apparatus of claim 23 wherein said means corotatively couplingsaid signaling member to said shaft include spline-and-groove meansbetween said signaling member and said shaft for allowing said signalingmember to move along said shaft between its said first and secondpositions.

27. The apparatus of claim 23 wherein said means corotatively couplingsaid signaling member to said shaft include spline-and-groove meansbetween said ing said motor back and forth in opposite rotativedirections so long as said signaling member is slowed below saidselected speed.

29. The apparatus of claim 28 wherein said motor is a reversible motor;and said control means include means operable upon slowing of said motorfor producing an electrical signal, and means responsive to said signalfor repetitively reversing said motor.

1. Apparatus adapted for transmitting data signals from a well bore tothe surface and comprising: a body adapted for connection in a pipestring and having a fluid passage arranged to carry debris-bearingfluids between the surface and well bore; first means including a firstsignal-producing member cooperatively arranged in said fluid passage fordirecting at least a portion of a fluid flowing therethrough along atleast one selected flow path; second means including a secondsignal-producing member cooperatively arranged in said fluid passageadjacent to said first member for rotation at a selected speed in aplane transverse to said flow path for repetitively obstructing saidflow path at periodic intervals to cyclically produce acoustic datasignals in a fluid flowing through said fluid passage; and third meansoperable upon at least slowing of said second member below said selectedspeed by fluid-borne solids flowing through said fluid passage formomentarily separating said signal-producing members to allow suchsolids to pass downstream of said signal-producing members.
 2. Theapparatus of claim 1 wherein said second means include an electricmotor, and means cooperatively coupling said second member to said motorfor rotation thereby as well as for movement between an operatingposition adjacent to said first member and a solids-clearing positionmore distant therefrom; and said third means include biasing meanscooperatively arranged for yieldably urging said second member normallytoward one of its said positions.
 3. The apparatus of claim 2 whereinsaid one position is said operating position of said second member. 4.The apparatus of claim 1 wherein said second means include an electricmotor, and means cooperatively coupling said second member for rotationthereby; and said third means include means cooperatively arranging oneof said members for longitudinal movement relative to the other of saidmembers between an operating position adjacent to said other member anda solids-clearing position more distant therefrom, and biasing meanscooperatively arranged for normally urging said one member toward saidother member and yieldable in response to slowing of said second memberbelow said selected speed by fluid-borne solids for allowing said onemember to move longitudinally away from said other member.
 5. Theapparatus of claim 1 wherein said second means include an electricmotor, a rotatable shaft drivingly coupled to said motor, meanscooperatively coupling said second member to said shaft for rotationthereby as well as for movement therealong between a signal-producingposition adjacent to said first member and a solids-clearing positionmore distant therefrom; and said third means include biasing meanscooperatively arranged between said shaft and said second member fornormally biasing said second member toward its said signal-producingposition and yieldable in response to at least one operating conditioncharacteristic of the rotational slowing of said second member forallowing said second member to move at least momentarily toward its saidsolids-clearing position.
 6. The apparatus of claim 1 wherein saidsecond means include a selectively reversible electrical motor, arotatable shaft drivingly coupled to sAid motor, and means cooperativelycoupling said second member to said shaft for rotation thereby as wellas for movement therealong between a first position adjacent to saidfirst member and at least a second position more distant therefrom; andsaid third means include biasing means cooperatively arranged betweensaid shaft and said second member normally biasing said second membertoward its said first position and yieldable in response to slowing ofsaid second member for allowing said second member to move at leastmomentarily toward its said second position, and circuit meansresponsive to the slowing of said second member for selectivelyreversing the rotational direction of said motor.
 7. The apparatus ofclaim 1 wherein said second means include a selectively reversibleelectrical motor, a rotatable shaft drivingly coupled to said motor,means cooperatively coupling said second member to said shaft forrotation thereby as well as for movement therealong between a firstposition adjacent to said first member and at least a second positionmore distant therefrom; and said third means include biasing meanscooperatively arranged between said shaft and said second membernormally biasing said second member toward its said first position andyieldable in response to slowing of the rotational speed of said secondmember for allowing said second member to move at least momentarilytoward its said second position, and circuit means responsive to theslowing of said second member and selectively operable for alternatelyreversing the rotational direction of said motor back and forth so longas said second member is slowed below said selected speed.
 8. Apparatusadapted for transmitting data to the surface during the drilling of aborehole and comprising: a body adapted for connection in a tubulardrill string and having a fluid passage arranged to conduct drillingfluids to a borehole-drilling device dependently coupled therebelow; aflow-directing member cooperatively arranged in said fluid passage andincluding at least one opening for directing drilling fluids flowingthrough said fluid passage along a selected axis; a flow-obstructingmember cooperatively arranged in said fluid passage for rotation in aplane transverse to said axis and including a plurality of alternatelydisposed openings and obstructions angularly spaced from one another andrespectively adapted to successively cut across said axis upon rotationof said flow-obstructing member; first means cooperatively coupled tosaid flow-obstructing member for rotating said flow-obstructing memberat at least one selected rotational speed for cyclically producingacoustic data signals in drilling fluids flowing through said fluidpassage; and second means operable in response to at least slowing ofsaid flow-obstructing member by lodging of fluid-borne debris betweensaid members for moving at least one of said members in relation to theother of said members to allow such debris to be carried downstream ofsaid members by drilling fluids flowing through said fluid passage. 9.The apparatus of claim 8 wherein said one member is saidflow-obstructing member.
 10. The apparatus of claim 9 wherein said firstmeans include motor means; and said second means include control meanscoupled to said motor means and responsive to slowing of saidflow-obstructing member below said selected speed for rotatively movingsaid flow-obstructing member back and forth in relation to saidflow-directing member so long as said flow-obstructing member is slowedbelow said selected speed.
 11. The apparatus of claim 9 wherein saidfirst means include a reversible electric motor; and said second meansinclude circuit means operable upon slowing of said motor means forproducing an electrical signal, and control means responsive to saidsignal for repetitively reversing said motor.
 12. The apparatus of claim9 wherein said first means include a motor, and a rotatable shaftcooperatively couplEd to said motor for rotation thereby; and saidsecond means include means co-rotatively coupling said flow-obstructingmember to said shaft for rotation thereby as well as for movement alongsaid shaft between a first position adjacent to said flow-directingmember and a second more-distant position away from said flow-directingmember, and biasing means normally urging said flow-obstructing membertoward its said first position and yieldable in response to theoccurrence of an operational condition indicative of the lodging offluid-borne debris between said members for allowing saidflow-obstructing member to move at least momentarily toward its saidsecond position.
 13. The apparatus of claim 12 wherein said operationalcondition is an increased pressure differential across said memberssufficient to move said flow-obstructing member toward its said secondposition.
 14. The apparatus of claim 12 wherein said second meansfurther include control means coupled to said motor and responsive toslowing of said flow-obstructing member below said selected speed forrotatively moving said flow-obstructing member back and forth inrelation to said flow-directing member so long as said flow-obstructingmember is slowed below said selected speed.
 15. The apparatus of claim 9wherein said first means include a motor, and a rotatable shaftcooperatively coupled to said motor for rotation thereby; and saidsecond means include means co-rotatively coupling said flow-obstructingmember to said shaft for rotation thereby as well as for longitudinalmovement along said shaft between a first position adjacent to saidflow-directing member and a second more-distant position away from saidflow-directing member, and biasing means normally urging saidflow-obstructing member toward its said first position and yieldable inresponse to the occurrence of an operational condition indicative of thelodging of fluid-borne debris between said members for allowing saidflow-obstructing member to move at least momentarily toward its saidsecond position.
 16. Apparatus adapted for measuring at least onedownhole condition while drilling a borehole and comprising: a bodytandemly coupled in a tubular drill string having a borehole-drillingdevice dependently coupled thereto and defining a fluid passage forcirculating drilling fluids between the surface and saidborehole-drilling device; data-signaling means on said body and adaptedfor producing electrical signals representative of at least one downholecondition; acoustic signaling means on said body and including anelectric motor coupled to said data-signaling means for selectiverotation in response to said electrical signals, a flow-directing memberin said fluid passage and having a plurality of angularly spacedopenings cooperatively arranged for directing drilling fluids inselected fluid paths along said fluid passage, and a rotatable signalingmember in said fluid passage and having a plurality of alternatelydistributed angularly-spaced openings and obstructions cooperativelyarranged to successively cross said fluid paths upon rotation of saidsignaling member for producing cyclic acoustic signals representative ofsaid electrical signals in drilling fluids flowing through said fluidpassage; first means cooperatively coupling said signaling member tosaid motor for rotation thereby at at least one selected rotationalspeed; and second means operable upon slowing of said signaling memberbelow said selected rotational speed by lodging of fluid-borne materialsbetween said members for moving said signaling member in relation tosaid flow-directing member to clear such fluid-borne materials fromtherebetween.
 17. The apparatus of claim 16 wherein said first meansinclude a rotatable shaft coupled to said motor; and said second meansinclude means co-rotatively coupling said signaling member to saidshaft, and control means coupled to said motor and responsive to slowingof said signaling member belOw said selected speed for alternatelydriving said motor back and forth in opposite rotative directions solong as said signaling member is slowed below said selected speed. 18.The apparatus of claim 16 wherein said signaling member is downstream ofsaid fluid-directing member.
 19. The apparatus of claim 18 wherein saidfirst means include a rotatable shaft coupled to said motor; and saidsecond means include means co-rotatively coupling said signaling memberto said shaft, and means operable upon increased pressure differentialsacross said members for shifting said signaling member along said shaftaway from said flow-directing member and operable upon the subsequentdecrease in such increased pressure differentials for shifting saidsignaling member along said shaft toward said flow-directing member. 20.The apparatus of claim 19 wherein said second means further includemeans co-rotatively coupling said signaling member to said shaft, andcontrol means coupled to said motor and responsive to slowing of saidsignaling member below said selected speed for alternately driving saidmotor back and forth in opposite rotative directions so long as saidsignaling member is slowed below said selected speed.
 21. The apparatusof claim 16 wherein said flow-directing member is fixed in relation tosaid body and is coaxially arranged in said fluid passage.
 22. Theapparatus of claim 16 wherein said flow-directing member is upstream ofsaid signaling member.
 23. The apparatus of claim 22 wherein said firstmeans include a rotatable shaft coupled to said motor; and said secondmeans include means co-rotatively coupling said signaling member to saidshaft for rotation thereby as well as for movement along said shaftbetween a first position adjacent to said flow-directing member and asecond more-distant position away from said flow-directing member, andbiasing means normally urging said signaling member toward its saidfirst position and yieldable in response to the occurrence of anoperational condition indicative of the lodging of fluid-borne debrisbetween said members for allowing said signaling member to move at leastmomentarily toward its said second position.
 24. The apparatus of claim23 wherein said operational condition is an increased pressuredifferential across said members sufficient to move said signalingmember toward its said second position.
 25. The apparatus of claim 24wherein said second means further include control means coupled to saidmotor and responsive to slowing of said signaling member below saidselected speed for alternately driving said motor back and forth inopposite rotative directions so long as said signaling member is slowedbelow said selected speed.
 26. The apparatus of claim 23 wherein saidmeans corotatively coupling said signaling member to said shaft includespline-and-groove means between said signaling member and said shaft forallowing said signaling member to move along said shaft between its saidfirst and second positions.
 27. The apparatus of claim 23 wherein saidmeans corotatively coupling said signaling member to said shaft includespline-and-groove means between said signaling member and said shaft forallowing said signaling member to move longitudinally along said shaftbetween its said first and second positions.
 28. The apparatus of claim27 wherein said operational condition is an increased pressuredifferential across said members sufficient to move said signalingmember toward its said second position; and said second means furtherinclude control means coupled to said motor and responsive to slowing ofsaid signaling member below said selected speed for alternately drivingsaid motor back and forth in opposite rotative directions so long assaid signaling member is slowed below said selected speed.
 29. Theapparatus of claim 28 wherein said motor is a reversible motor; and saidcontrol means include means operable upon slowing of said motor forproducing an electrical sigNal, and means responsive to said signal forrepetitively reversing said motor.